
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';

// class Square extends React.Component {
//     render() {
//         return (
//             <button className="square" onClick={() => {this.props.onClick();}}>
//                 {this.props.value}
//             </button>
//         );
//     }
// }

function Square(props) {
    return (
        <button className="square" onClick={props.onClick}>
            {props.value}
        </button>
    );
}


class Board extends React.Component {
    // constructor(props) {
    //     super(props);
    //     this.state = {
    //         squares: Array(9).fill(null),
    //         xIsNext: true
    //     };
    // }
    renderSquare(i) {
        return (<Square
            value={this.props.squares[i]}
            onClick={() => { this.props.onClick(i); }}
        />);
    }
    render() {
        // let status = null;
        // let _winner = calculateWinner(this.state.squares);
        // if(_winner) {
        //     status = 'Winner: ' + _winner;
        // } else {
        //     status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
        // }

        return (
            <div>
                {/* <div className="status">{status}</div> */}
                <div className="board-row">
                    {this.renderSquare(0)}
                    {this.renderSquare(1)}
                    {this.renderSquare(2)}
                </div>
                <div className="board-row">
                    {this.renderSquare(3)}
                    {this.renderSquare(4)}
                    {this.renderSquare(5)}
                </div>
                <div className="board-row">
                    {this.renderSquare(6)}
                    {this.renderSquare(7)}
                    {this.renderSquare(8)}
                </div>
            </div>
        );
    }
}

class Game extends React.Component {
    constructor(props) {
        super(props);
        this.state = {
            history: [
                {
                    squares: Array(9).fill(null)
                }
            ],
            stepNumber: 0,
            xIsNext: true
        };
    }
    render() {
        const _history = this.state.history;
        // const current = _history[_history.length - 1];
        const current = _history[this.state.stepNumber]; // 之前是因为这里的值没改正确，所以导致“棋盘”没有随步骤清理。
        const winner = calculateWinner(current.squares);

        let status;
        if (winner) {
            status = 'Winner :' + winner;
        } else {
            status = 'Next player : ' + (this.state.xIsNext ? 'X' : 'O');
        }

        const moves = _history.map((step, move) => {
            const desc = move ? 'Go to move #' + move : 'Go to game start';
            return (
                <li key={move}>
                    <button onClick={() => {this.jumpTo(move)}}>{desc}</button>
                </li>
            );
        });

        return (
            <div className="game">
                <div className="game-board">
                    <Board 
                        squares={current.squares}
                        onClick={(i) => {this.handleClick(i)}}
                    />
                </div>
                <div className="game-info">
                    <div>{status}</div>
                    <ol>{moves}</ol>
                </div>
            </div>
        );
    }
    handleClick(i) {
        const _history = this.state.history.slice(0, this.state.stepNumber + 1);
        //const current = _history[_history.length - 1];
        const current = _history[this.state.stepNumber];
        const _squares = current.squares.slice();
        if(_squares[i] || calculateWinner(_squares)) {
            return;
        }
        _squares[i] = this.state.xIsNext ? 'X' : 'O';
        // this.state.squares = squares;
        this.setState({
            history: _history.concat([{
                squares: _squares
            }]),
            stepNumber: _history.length, // `_history`总是比`this.state.history`小`1`,因为`_history.concat(...)`
            xIsNext: !this.state.xIsNext
        });
    }
    jumpTo(step) {
        this.setState({
            stepNumber: step,
            xIsNext: (step % 2) === 0,
        });
    }
}

// ========================================

ReactDOM.render(
    <Game />,
    document.getElementById('root')
);

function calculateWinner(squares) {
    const lines = [
        [0, 1, 2],
        [3, 4, 5],
        [6, 7, 8],
        [0, 3, 6],
        [1, 4, 7],
        [2, 5, 8],
        [0, 4, 8],
        [2, 4, 6],
    ];
    for (let i = 0; i < lines.length; i++) {
        const [a, b, c] = lines[i];
        if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
            return squares[a];
        }
    }
    return null;
}

